Synthesis and Electrochemical Properties of Ni_xCo_3−xO₄ with Porous Hierarchical Structures for Na-Ion Batteries

Abstract

Highly crystallized cubic Ni_xCo_3−xO₄ with porous hierarchical structures was synthesized through a simple coprecipitation method followed by calcination at temperatures above 400°C in air. The performances of the samples as anode materials for Na-ion batteries were evaluated. At 100 mA g⁻¹ in the 50th cycle, the nanorod-like Co₃O₄ sample that was calcined at 400°C delivered a discharge capacity of 169.4 mA h g⁻¹, which corresponded to 27.7% of the second discharge capacity. By contrast, at 100 mA g⁻¹ in the 50th cycle, the flower-like Ni_0.3Co_2.7O₄ sample delivered a discharge capacity of 274.6 mA h g⁻¹, which corresponded to 42.9% of the second discharge capacity. The improved performance shown by this anode material was attributed to the formation of additional mesopores and the stabilization of cubic Ni_0.3Co_2.7O₄ after doping with Ni²⁺ ions. The above results showed that the electrochemical properties of metal oxide electrode materials can be effectively improved by controlling compositions and nanostructures.